1. Field of the Invention
The present invention relates to a control means for hydraulic clutches and, more particularly, to a control means for a change-over valve for hydraulic clutches through which a pressurized oil is supplied into a hydraulic clutch whereby a rotary driving force from the engine is connected to or disconnected from a PTO drive shaft of, for example, a tractor.
2. Description of the Prior Art
A conventional hydraulic clutch of this kind is generally provided with a rotary spool type or slide spool type change-over valve to which a control handle is connected via a lever. The hydraulic clutch is let in and out while opening and closing an oil passage in the change-over valve by operating the control handle to rotate or slide the spool. When the control handle is slowly operated, the spool is rotated or slid slowly. In this case, the clutch is in a half-operated state for an unduly long time. This causes the lining of the clutch to be worn early or causes inconveniences due to the unnecessary heat generated. Especially, a clutch having a paper lining which has a low resistance to heat is easily damaged.